An outdoor unit of a known air conditioner includes, for example, a unit body formed in a rectangular parallelepiped shape, a propeller fan and a fan motor for rotationally driving the propeller fan, which are installed in the unit body, a heat exchanger installed in an L-shape and extending along a side surface and a rear surface of the unit body, a bell mouth installed radially outward of the propeller fan, and a partition plate (also called a separator) disposed to partition an installation space of a compressor for supplying a refrigerator to the heat exchanger and an installation space of the propeller fan and to guide an airstream from the heat exchanger toward the bell mouth.
In the known air conditioner constructed as described above, when the propeller fan is rotated, an airstream is caused to pass through the heat exchanger from the outside of the unit body to be subjected to heat exchange and to be discharged to the outside of the unit body after passing through the bell mouth.
Recently, more power saving and quieter operation have been demanded in air conditioners and, to meet those demands, proposals have been made on configurations adapted for reducing noise of a propeller fan, which is a source of aerodynamic noise. In one example of the proposals, a bell mouth on a separator side is extended toward an upstream side to smoothen an airstream, thus increasing efficiency of the propeller fan and reducing the noise (see Patent Document 1). In another example of the proposals, to control the airstream flowing into a circular propeller fan even in a unit having a rectangular parallelepiped shape, the radius of curvature of the bell mouth on a sucking side is changed depending on the size of a surrounding space (see Patent Document 2). In still another example of the proposals, a soundproofing partition plate is formed in a duct-like or hood-like shape, thus causing the airstream from the heat exchanger to smoothly flow into the propeller fan (see Patent Document 3).    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-77585 (pages 4-5 and FIG. 1)    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 3-168395 (page 2 and FIGS. 2 and 3)    [Patent Document 3] Japanese Unexamined Patent Application Publication No. 10-238815 (page 3 and FIGS. 1 and 2)